Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, monolithic windows, and/or the like. In certain example instances, designers of coated articles often strive for a combination of high visible transmission, substantially neutral color, low emissivity (or emittance), low sheet resistance (Rs), low U-values in the context of IG window units, and/or low specific resistivity. High visible transmission and substantially neutral color may permit coated articles to be used in applications where these characteristics are desired such as in architectural or vehicle window applications, whereas low-emissivity (low-E), low sheet resistance, and low specific resistivity characteristics permit such coated articles to block significant amounts of IR radiation so as to reduce for example undesirable heating of vehicle or building interiors.
Consider a typical coated article with the following layer stack. This coated article is suitable for use in an IG (insulation glass) window unit. For the coated article listed below, the coating includes layers that are listed from the glass substrate outwardly.
Layer GlassThickness ({acute over (Å)})TiOx140{acute over (Å)}SnOx100ÅZnAlOx70{acute over (Å)}Ag118{acute over (Å)}NiCrOx20{acute over (Å)}SnOx223ÅSiNx160{acute over (Å)}
The silver (Ag) layer of the above coated article has a thickness of 118 angstroms (Å) and a sheet resistance (Rs) of 4.6 ohms/square. This translates into a specific resistivity (Rs multiplied by thickness of the IR reflecting layer) for the silver IR reflecting layer of 5.43 micro-ohms·cm.
While the aforesaid specific resistivity (SR) of the silver IR reflecting layer is adequate in many situations, it would be desirable to improve upon the same. For example, if the specific resistivity (SR) of the silver layer could be lowered, then the coating could realize improved thermal properties (e.g. lower U-value, lower emittance, and/or the like) given an IR reflecting layer of the same thickness. Thus, a lower specific resistance of the IR reflecting layer(s) is desirable, as it permits thermal properties of the coating to be improved.
In view of the above, it will be appreciated that there exists a need in the art for a coated article including a coating which has good thermal properties. Certain example embodiments of this invention relate to a coated article which permits thermal properties to be improved.
In certain example embodiments of this invention, it has surprisingly been found that the provision of a layer comprising titanium oxide over an IR reflecting layer (e.g., of silver or the like) unexpectedly improves the quality of the IR reflecting layer thereby permitting the coated article to realized improved thermal properties with a given thickness of the IR reflecting layer. In certain example embodiments, the titanium oxide layer may be provided over the IR reflecting, layer, and may be located between a first layer comprising NiCrOx and a second layer comprising a metal oxide such as tin oxide. Even though the titanium oxide need not be directly contacting the IR reflecting layer, it still surprisingly improves the quality of the underlying IR reflecting layer thereby permitting thermal properties of the coating to be improved.
In certain example embodiments of this invention, the provision of the titanium oxide layer over the IR reflecting layer surprisingly results in an IR reflecting layer with a lower specific resistivity (SR). The lower the SR of an IR reflecting layer, the lower the emittance of the coated article with an IR reflecting layer of a given thickness. Likewise, the lower the SR of an IR reflecting layer, the lower the U-value of an IG unit including a similar coating having an IR reflecting layer of a given thickness. Thus, lowering the SR of an IR reflecting layer permits thermal properties of a coated article to be improved given an IR reflecting layer(s) of like thickness. Alternatively, lowering the SR of an IR reflecting layer permits thermal properties of a coated article to remain substantially the same while reducing the thickness of the IR reflecting layer(s) which may be desirable for increasing visible transmission or the like in certain situations.
Thus, it can be seen that lowering the SR of an IR reflecting layer is advantageous. As discussed herein, it has been found that the provision of the titanium oxide layer over the IR reflecting layer surprisingly results in an IR reflecting layer with a lower SR.
In certain example embodiments of this invention, the titanium oxide layer over the IR reflecting layer may be oxidation graded. In certain example embodiments, the titanium oxide layer may be more oxided at a location further from the IR reflecting layer than at a location closer to the IR reflecting layer. Surprisingly, this has been found to improve the adhesion of the titanium oxide layer to the underlying layer such as a layer comprising NiCrOx or silver. In other example embodiments of this invention, the titanium oxide layer may be more oxided at a location proximate a central portion of the layer than at respective locations closer to the upper and lower surfaces of the layer. Again, this has been found to improve the adhesion of the layer comprising titanium oxide to the layers below and above the titanium oxide.
In certain example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising a dielectric layer; an infrared (IR) reflecting layer comprising silver located on the substrate over the dielectric layer; a layer comprising an oxide of Ni and/or Cr located over and directly contacting the IR reflecting layer comprising silver; a layer comprising titanium oxide located over and directly contacting the layer comprising the oxide of Ni and/or Cr; a layer comprising a metal oxide located over and directly contacting the layer comprising titanium oxide; and a layer comprising silicon nitride located over the layer comprising the metal oxide.
In other example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising a layer comprising zinc oxide; an infrared (IR) reflecting layer comprising silver located on the substrate over and contacting the layer comprising zinc oxide; a layer comprising titanium oxide located over the IR reflecting layer; a layer comprising silicon nitride and/or metal oxide located over the layer comprising titanium oxide; and wherein the IR reflecting layer has a specific resistivity (SR) of no greater than 5.0 micro-ohms·cm.
In still further example embodiments of this invention, there is provided a method of making a coated article, the method comprising providing a glass substrate; forming a dielectric layer on the substrate; forming an IR reflecting layer comprising silver on the substrate over at least the dielectric layer; depositing a layer comprising titanium oxide on the substrate over the IR reflecting layer in a manner so that the layer comprising titanium oxide as deposited is more oxided at a location therein further front the IR reflecting layer than at a location closer to the IR reflecting layer.